How to find the coordinates of a line parallel to another on the same layer
Hi,
You can try something like this:
[CommandMethod("FINDPARALLEL")]
public static void FindClosestParallelLineCmd()
{
var doc = Application.DocumentManager.MdiActiveDocument;
var db = doc.Database;
var ed = doc.Editor;
var options = new PromptEntityOptions("\nSelect Line: ");
options.SetRejectMessage("Must be a Line.");
options.AddAllowedClass(typeof(Line), true);
var result = ed.GetEntity(options);
if (result.Status != PromptStatus.OK)
return;
using (var tr = db.TransactionManager.StartTransaction())
{
var source = (Line)tr.GetObject(result.ObjectId, OpenMode.ForRead);
if (TryFindParallelLine(source, tr, out LineSegment3d line))
{
ed.WriteMessage("\nStart point: {0:0.00} End point: {1:0.00}", line.StartPoint, line.EndPoint);
}
else
{
ed.WriteMessage("\nNone parallel line");
}
tr.Commit();
}
}
static bool TryFindParallelLine(Line source, Transaction tr, out LineSegment3d line)
{
string layer = source.Layer;
var segment = new LineSegment3d(source.StartPoint, source.EndPoint);
var direction = segment.Direction;
var segments =
((BlockTableRecord)tr.GetObject(source.OwnerId, OpenMode.ForRead))
.Cast<ObjectId>()
.Where(id => id != source.ObjectId && id.ObjectClass.DxfName == "LINE")
.Select(id => (Line)tr.GetObject(id, OpenMode.ForRead))
.Where(l => l.Layer == layer)
.Select(l => new LineSegment3d(l.StartPoint, l.EndPoint))
.Where(s => s.Direction.IsParallelTo(direction));
if (segments.Any())
{
line = segments.Aggregate((s1, s2) =>
(s1.GetDistanceTo(segment) < s2.GetDistanceTo(segment)) ? s1 : s2);
return true;
}
else
{
line = null;
return false;
}
}
Hi, thank you so much for your help.
Your code works perfectly but I asked myself: how can I find the perpendicular distance between the two parallel lines?
I tried like this:
ed.WriteMessage (vbLf & "Perpendicular distance beetwen line1 and line2:" & line.StartPoint.DistanceTo (source.GetClosestPointTo (line.StartPoint, False)))
What I have written only works in three cases:
1. when the two lines are inclined at a certain angle;
2. when the two lines have the same length;
3. when I select the longest line.
If the two lines, horizontal or vertical, have a different length and I select the shorter line, I get the distance between points A and C and not the perpendicular distance between the two lines.
Where do you think I'm wrong?
Thanks a lot, bye.
Accepted solution
As you certainly noticed, the code uses the LineSegment3d type which exposes a GetDistanceTo method. This method is used to find the closest parallel line.
[CommandMethod("FINDPARALLEL")]
public static void FindClosestParallelLineCmd()
{
var doc = Application.DocumentManager.MdiActiveDocument;
var db = doc.Database;
var ed = doc.Editor;
var options = new PromptEntityOptions("\nSelect Line: ");
options.SetRejectMessage("Must be a Line.");
options.AddAllowedClass(typeof(Line), true);
var result = ed.GetEntity(options);
if (result.Status != PromptStatus.OK)
return;
using (var tr = db.TransactionManager.StartTransaction())
{
var source = (Line)tr.GetObject(result.ObjectId, OpenMode.ForRead);
if (TryFindParallelLine(source, tr, out LineSegment3d line, out double distance))
{
ed.WriteMessage(
"\nStart point: {0:0.00} End point: {1:0.00}\nDistance = {2:0.00}",
line.StartPoint,
line.EndPoint,
distance);
}
else
{
ed.WriteMessage("\nNone parallel line");
}
tr.Commit();
}
}
static bool TryFindParallelLine(Line source, Transaction tr, out LineSegment3d line, out double distance)
{
string layer = source.Layer;
var segment = new LineSegment3d(source.StartPoint, source.EndPoint);
var direction = segment.Direction;
var segments =
((BlockTableRecord)tr.GetObject(source.OwnerId, OpenMode.ForRead))
.Cast<ObjectId>()
.Where(id => id != source.ObjectId && id.ObjectClass.DxfName == "LINE")
.Select(id => (Line)tr.GetObject(id, OpenMode.ForRead))
.Where(l => l.Layer == layer)
.Select(l => new LineSegment3d(l.StartPoint, l.EndPoint))
.Where(s => s.Direction.IsParallelTo(direction));
if (segments.Any())
{
line = segments.Aggregate((s1, s2) =>
(s1.GetDistanceTo(segment) < s2.GetDistanceTo(segment)) ? s1 : s2);
distance = line.GetDistanceTo(segment);
return true;
}
else
{
line = null;
distance = -1.0;
return false;
}
}